逐次逼近ADC，可选择工作于12位，也可工作于8位。转换后的数据有两种 读出方式：12位一次读出；８位、４位两次读出。 具有可控三态输出缓冲器，逻辑电平为TTL电平。-Successive approximation ADC, alternative work at 12, but also can work in 8-bit. Converted to read out the data in two ways: first read 12 8-bit, 4 twice read.